This invention relates to a process for the preparation of novel Vinylic Hindered Amine Light Stabilizers (HALS) having general formula (I): 
wherein:
R1 is C1 to C8: alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (all linear and branched), allyl, acyl, cycloalkyl (cyclopentyl, cyclohoxyl or cumyl: linear and branched); R2 is hydrogen or methyl, R3 is Vinyl, C1-C4 vinyl alkyl [H2Cxe2x95x90C(R4)C1-C4], R4 is H, C1-C4 alkyl or alkyl phenyl and R5 is H or C1-C4 alkyl, X is O, NH, C1-C8 linear or branched chain or alkylamino.
Monomeric hindered amine light stabilizers are gaining much more importance to stabilize the polyolefins and diene elastomers. Natural and synthetic polymers in common use are susceptible to photo-oxidative degradation upon exposure to natural and artificial weathering. The deterioration of these polymeric materials is mainly due to the UV portion of sunlight reaching the earth surface. The net result of degradation is the loss in the Molecular weight and macroscopic physical properties. Polyolefins and unsaturated synthetic elastomers, being highly sensitive to oxidation, require the addition of stabilizers to provide protection during processing, storage and end-use. The low Molecular weight stabilizers are easily lost from the polymer through evaporation, migration and extraction but, the compatible and mobile stabilizers usually give the best protection. In order to avoid this loss polymer-bound and polymeric stabilizers have been devised. Moreover, since the degradation of a polymer commences from the surface and slowly proceeds into the matrix of the polymeric substrate, the stabilizers are therefore expected to be most potent if they are concentrated at the surface. Therefore, they should be anchored covalently to the polymer surface. Monomeric light stabilizers thus prove to be the best choice to attain the desired photostability.
A discrete literature on the synthesis of the vinylic derivatives of HALS is available; some of these methods are quite trivial and employ complex routes using expensive reagents. Following patents and literature: DE 2950067 (January 1981); DE 2642446 (March 1978); F. E. Karrer, Markromol. Chem. 181, 595 (German) 1980, N. S. Prostakov, A. V. Varlomov and G. A. Vasilev, Khim., Geterotsikl. Soedin., 6, 787 (Russian) 1977, JP 53015385 (February 1978); D. V. Sokolov, M. N. Akimova, K. D. Praliev, V. M. Kurilenko, Zh. N. Khlienko and K. M. Moiseeva, Khim.Farm. Zh. 11, 47 (Russian) 1977; P. Hrdlovic and S. Chmela, Int. J. Polym. Mater., 13, 245 (1990); J. Pan, Z. Yang, L. Tong, W. Lau, W. Y. Wayne and C. S. Lee, Polym. Degrad. Stab. 44, 85, 1994; disclose the preparation and the mechanism of application of HALS derivatives.
Some of the authors have reported vinylic derivatives of HALS as polymerizable light stabilizers wherein, the vinyl group is attached to the hindered nitrogen atom. One of the vinylic derivative of HALS having formula 
is disclosed in the patent EP 24999145 A1 (December 1987). Upon UV irradiation under atmospheric condition; the hindered nitrogen bearing the vinyl group gets converted into nitroxyl radical (Nxe2x80x94O*). 
As a result of which the hindered amine moiety gets detached from the covalently bonded vinyl group attached to the surface and is thus prone to be lost due to leaching/extraction/evaporation (shown in the Scheme 1), making it inefficient, The objective of the present invention is therefore, to provide a process for the preparation of novel vinylic HALS, which can the firmly bound to the polymer surface. Moreover, this class of monomeric HALS are known to be compatible with polyolefins, polystyrene and diene elastomers and can even be co-polymerized in a desired proportion to obtain xe2x80x98in chainxe2x80x99 and xe2x80x98chain endxe2x80x99 radical scavengers.
According to the present invention a process for preparation of the said HALS of formula 1, which comprises refluxing the solution of compound having general formula (II) 
wherein R1 is hydrogen (H), R2 is hydrogen and methyl, R3 is H, C1-C4 alkyl, X is OH, NH2, C1-C8 alkylhydroxy and alkylamino (linear or branched) an organic solvent containing an carbonyl compound having general formula (III) 
wherein: R1xe2x95x90R2xe2x95x90H, C1 to C8: alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (linear and branched), allyl, cycloalkyl (cyclopentyl, cyclohexyl or cumyl: linear and branched) in an organic acid for 4-6 hrs, followed by adjusting the pH of the refluxed reaction mixture to 7.0 to 9.0, extracting in an organic solvent and removing the solvent to obtain the compound having formula (IV) 
wherein: R1 is C1 to C8: alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (linear and branched), allyl, acyl, cycloalkyl (cyclopentyl, cyclohexyl or cumyl: linear and branched); R2 is hydrogen and methyl, R3 is H, C1-C4 alkyl, X is OH, NH2, C1-C8 alkylhydroxy and alkylamino(linear or branched. Reacting the mixture of a catalyst with a compound having formula (IV) in a dry organic solvent in an inert atmosphere adding an organic base under continuous stirring, adding a compound having a general formula (V) 
wherein R is H, C1-C4 alkyl or alkyl phenyl, under stirring and continuing the stirring for a further period of 8 to 12 hrs, quenching with water at a temperature ranging between 0 to 4xc2x0 C., extracting in an organic solvent, neutralizing the solvent fraction with an inorganic base, evaporating the solvent to obtain the final product. In one of the embodiments of the present invention, the organic acid used for preparing the solution of the compound having formula (II) is selected from formic acid, acetic acid and propanoic acid.
Accordingly the invention provides a process for the preparation of Vinylic Hindered Amine Light Stabilizers having formula 
(I) which comprises refluxing the solution of compound of general formula (II),
(II) in an organic solvent containing carbonyl compound of formula (III) for 4-6 hrs, adjusting the pH of the refluxed reaction mixture to 7.0 to 9.0, extracting the reaction product in an organic solvent, removing the solvent to obtain the compound having formula (IV) reacting the above compound of formula (IV) with a catalyst in a dry organic solvent in an inert atmosphere, adding an organic base to the above reaction mixture under continuous stirring, along with a compound having a general formula (V) under stirring and continuing the stirring for a further period of 8 to 12 hrs, quenching the above reaction with water at a temperature ranging between 0 to 4xc2x0 C., extracting the resultant compound in an organic solvent, neutralizing the solvent fraction with an inorganic base and evaporating the solvent to obtain the final product having formula (I).
In other embodiment of the invention the organic acid used for preparing the solution of the compound having formula (II) is selected from formic acid, acetic acid and propanoic acid.
In one of the other embodiments of the present invention, the carbonyl compound having formula (III) used is selected from the group consisting of formalin, formaldehyde, acetaldehyde, benzaldehyde, methyl ethyl, ketone, methyl benzyl ketone and cyclohexyl methyl ketone.
In yet another embodiments of the present invention, the organic solvent used for extracting the products is selected from the group consisting of used from diethyl ether, dichloromethane, ethyl acetate, and benzene.
In yet another embodiment of the present invention the catalyst used is alkyl substituted amino pyridines selected from the group consisting of N,N-dimethyl aminopyridine, 4-aminopyridine and 2-mercaptobenzoxazole.
In another embodiment the dry organic solvent used to dissolve the catalyst and compound (IV) is selected from the group consisting of dichloromethane, dochloroethane, carbon tetrachloride, cyclohexane, n-hexane and chlorobenzene.
In another embodiment the compound (V) added to react with compound (IV) is selected from the group consisting of acryloyl chloride, methacryloyl chloride, pentenoyl chloride and 3-butenoyl chloride-3-phenyl.
In yet another embodiment the base used is selected from aliphatic and aromatic amine selected from the group consisting from triethyl amine, trimethyl amine, 2,6-lutidine and pyridine.
In yet another embodiment of the invention the inorganic base used to neutralize the solvent fraction containing the product is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate.
In yet another embodiment of the present invention wherein the inert gasused is selected from Nitrogen, Argon.
HALS monomers and some of its derivatives may be prepared by any of the methods known in the art including those disclosed in Patents No. JP 53015385 28 (July 1978), Swiss CH 610898 (May 15, 1979), Swiss CH 605927 (October 1978), Brit. GB 1492494 (November 1977) and Literature: T. Tsuchiya and H. Sashida, Heterocycles, 14, 1925-8 (1980). All these patents are incorporated herein by reference. HALS namely 2,2,6,6-tetramethyl piperidine and 2,2,6,6-tetramethyl-4-piperidinol may be prepared by synthetic route disclosed by W. B. Lutz, S. Lazams and R. I. Meltzer, J. Org. Chem., 14, 530 (1949). All these patents and literature are incorporated herein by reference.